The present invention relates to valve assemblies for controlling the flow of fuel gas to a burner and particularly, to such valve assemblies for controlling gas flow to cooking ovens, particularly the type of ovens employed in recreational vehicles utilizing liquid petroleum (LP) bottled gas. LP gas burning appliances of the type employed in recreational vehicles typically utilize a standing pilot flame for igniting the main oven burner with a flame sensor disposed to sense presence of the pilot flame for opening a main control valve to permit flow to the main burner only when presence of flame has been detected at the pilot burner. When the main burner has been ignited for cooking purposes, a secondary control valve is employed in the fuel gas line to thereafter control flow to the main burner in order to modulate the temperature in the oven about a desired set temperature for cooking. The secondary valve is typically thermostatically controlled by a fluid pressure sensing element connected to a temperature sensor disposed to sense the ambient temperature in the oven.
Presently, commercially available LP gas ovens for recreational vehicles combine the function of the thermostatically controlled secondary burner valve with a manually operated valve for shutting off all gas to the pilot and main burner or shutting off gas to the main burner, but providing flow to the pilot for igniting the standing pilot upon start-up of the appliance. Heretofore, the commercially available thermostatic control valves for LP gas ovens provided a thermostatic valve assembly which permitted gas to flow to the pilot burner and the main burner ignition valve when the thermostatic shut-off valve was placed in the "PILOT" position. In the event that the main burner ignition valve was defective, and either failed to close in the absence of a standing pilot flame, or closed, but leaked fuel gas flow to the main burner in the closed position, a situation was created wherein, upon setting the thermostatic valve to the PILOT position, unwanted gas could flow prematurely to the main burner; and, upon ignition of the pilot, a condition could exist where there was serious hazard of explosion. Such occurrences have been experienced in field service with LP gas ovens; and, it has thus been desirable to provide a thermostatic gas valve which provided, in the PILOT position, gas flow only to the pilot burner and prevented any gas flow to the main burner control valve.
Heretofore, in order to provide separate valving of gas flow from the LP gas source to the main and pilot burners required separate thermostatically controlled valves. This arrangement has proven to be costly and has required the installation of extra tubing and gas lines within the appliance. It has thus been desired to find a way or means of providing a thermostatic shut-off valve assembly for an LP gas oven in which the gas to the main burner and the gas flow to the pilot burner were both controlled individually and separately by a single manually controllable shut-off valve.